From 7426d8d807ebfd19833aefa13be4236cedf4a062 Mon Sep 17 00:00:00 2001
From: Cameron Hart <cam@bitshifter.net.nz>
Date: Fri, 1 Jan 2016 18:05:32 +1100
Subject: [PATCH] Support for scalar on the lhs of arithmetic operators

---
 src/macros.rs   | 32 ++++++++++++++++++++++++++++++++
 src/vector.rs   | 11 +++++++++++
 tests/vector.rs | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)

diff --git a/src/macros.rs b/src/macros.rs
index ed2223a..fc5d43f 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -95,6 +95,38 @@ macro_rules! impl_operator {
             }
         }
     };
+    // When the left operand is a scalar
+    ($Op:ident<$Rhs:ident<$S:ident>> for $Lhs:ty {
+        fn $op:ident($lhs:ident, $rhs:ident) -> $Output:ty { $body:expr }
+    }) => {
+        impl $Op<$Rhs<$S>> for $Lhs {
+            type Output = $Output;
+            #[inline]
+            fn $op(self, other: $Rhs<$S>) -> $Output {
+                let ($lhs, $rhs) = (self, other); $body
+            }
+        }
+    };
+}
+
+macro_rules! impl_scalar_ops {
+    ($VectorN:ident<$S:ident> { $($field:ident),+ }) => {
+        impl_operator!(Add<$VectorN<$S>> for $S {
+            fn add(scalar, vector) -> $VectorN<$S> { $VectorN::new($(scalar + vector.$field),+) }
+        });
+        impl_operator!(Sub<$VectorN<$S>> for $S {
+            fn sub(scalar, vector) -> $VectorN<$S> { $VectorN::new($(scalar - vector.$field),+) }
+        });
+        impl_operator!(Mul<$VectorN<$S>> for $S {
+            fn mul(scalar, vector) -> $VectorN<$S> { $VectorN::new($(scalar * vector.$field),+) }
+        });
+        impl_operator!(Div<$VectorN<$S>> for $S {
+            fn div(scalar, vector) -> $VectorN<$S> { $VectorN::new($(scalar / vector.$field),+) }
+        });
+        impl_operator!(Rem<$VectorN<$S>> for $S {
+            fn rem(scalar, vector) -> $VectorN<$S> { $VectorN::new($(scalar % vector.$field),+) }
+        });
+    };
 }
 
 macro_rules! impl_assignment_operator {
diff --git a/src/vector.rs b/src/vector.rs
index 91abfcb..0d47c75 100644
--- a/src/vector.rs
+++ b/src/vector.rs
@@ -244,6 +244,7 @@ macro_rules! impl_vector {
         impl_operator!(<S: BaseNum> Mul<$VectorN<S> > for $VectorN<S> {
             fn mul(lhs, rhs) -> $VectorN<S> { $VectorN::new($(lhs.$field * rhs.$field),+) }
         });
+
         impl_assignment_operator!(<S: BaseNum> MulAssign<S> for $VectorN<S> {
             fn mul_assign(&mut self, scalar) { $(self.$field *= scalar);+ }
         });
@@ -285,10 +286,20 @@ macro_rules! impl_vector {
     }
 }
 
+macro_rules! impl_vector_scalar_ops {
+    ($($S:ident)*) => ($(
+        impl_scalar_ops!(Vector2<$S> { x, y });
+        impl_scalar_ops!(Vector3<$S> { x, y, z });
+        impl_scalar_ops!(Vector4<$S> { x, y, z, w });
+    )*)
+}
+
 impl_vector!(Vector2<S> { x, y }, 2, vec2);
 impl_vector!(Vector3<S> { x, y, z }, 3, vec3);
 impl_vector!(Vector4<S> { x, y, z, w }, 4, vec4);
 
+impl_vector_scalar_ops!(usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64);
+
 impl_fixed_array_conversions!(Vector2<S> { x: 0, y: 1 }, 2);
 impl_fixed_array_conversions!(Vector3<S> { x: 0, y: 1, z: 2 }, 3);
 impl_fixed_array_conversions!(Vector4<S> { x: 0, y: 1, z: 2, w: 3 }, 4);
diff --git a/tests/vector.rs b/tests/vector.rs
index cd76a1b..4950021 100644
--- a/tests/vector.rs
+++ b/tests/vector.rs
@@ -33,6 +33,44 @@ fn test_from_value() {
     assert_eq!(Vector4::from_value(76.5f64), Vector4::new(76.5f64, 76.5f64, 76.5f64, 76.5f64));
 }
 
+macro_rules! test_ops {
+    ($VectorN:ident { $($field:ident),+ }, $s:expr, $v:expr) => (
+        // add
+        assert_eq!($v + $s, $VectorN::new($($v.$field + $s),+));
+        assert_eq!($s + $v, $VectorN::new($($s + $v.$field),+));
+        assert_eq!($v + $s, $s + $v);
+        // sub
+        assert_eq!($v - $s, $VectorN::new($($v.$field - $s),+));
+        assert_eq!($s - $v, $VectorN::new($($s - $v.$field),+));
+        assert_eq!($v - $s, -($s - $v));
+        // mul
+        assert_eq!($v * $s, $VectorN::new($($v.$field * $s),+));
+        assert_eq!($s * $v, $VectorN::new($($s * $v.$field),+));
+        assert_eq!($v * $s, $s * $v);
+        // div
+        assert_eq!($v / $s, $VectorN::new($($v.$field / $s),+));
+        assert_eq!($s / $v, $VectorN::new($($s / $v.$field),+));
+        // rem
+        assert_eq!($v % $s, $VectorN::new($($v.$field % $s),+));
+        assert_eq!($s % $v, $VectorN::new($($s % $v.$field),+));
+    )
+}
+
+#[test]
+fn test_ops() {
+    let a = [3.0f32, 4.0f32, 5.0f32, 6.0f32];
+    let s = 2.0f32;
+
+    let v4 = Vector4::from(a);
+    test_ops!(Vector4 { x, y, z, w }, s, v4);
+
+    let v3 = v4.truncate();
+    test_ops!(Vector3 { x, y, z }, s, v3);
+
+    let v2 = v3.truncate();
+    test_ops!(Vector2 { x, y }, s, v2);
+}
+
 #[test]
 fn test_dot() {
     assert_eq!(Vector2::new(1isize, 2isize).dot(Vector2::new(3isize, 4isize)), 11isize);